An antenna of the aforementioned type is disclosed in French Patent Specification No. 2015415, British Patent No. 964,458 and U.S. Pat. No. 3,099,836. Such antennas have a relatively large aperture as well as, for that reason, a relatively coarse resolution. It is due to these circumstances that objects embedded in the earth of small geometric dimensions can be located. However, no exact determination can be made regarding the size, shape and position of such small objects. If, on the other hand, an antenna of small aperture is selected, only a short search pulse can be transmitted, which in the case of wet ground and correspondingly increased attenuation, cannot penetrate sufficiently deeply to detect small objects.